30,610 research outputs found
Magnetic and Electronic Phase Diagram and Superconductivity in the Organic Superconductors k-(BEDT-TTF)2X
The magnetic susceptibility of the organic superconductors -(h8 or
d8-ET), Cu(NCS) and Cu[N(CN)]Br has been studied. A
metallic phase below 37 38 K for Cu[N(CN)]Br and
46 50 K for Cu(NCS) has an anisotropic temperature
dependence of the susceptibility and the charge transport. Partial
charge-density-wave or charge fluctuation is expected to coexist with the
metallic phase instead of the large antiferromagnetic fluctuation above
. The phase diagram and the superconductivity of -(ET)
are discussed in connection with this phase.Comment: 5 pages, 4figures, REVTeX, references are corrected, accepted for
pubication in Phys. Rev.
Restrictions of generalized Verma modules to symmetric pairs
We initiate a new line of investigation on branching problems for generalized
Verma modules with respect to complex reductive symmetric pairs (g,k). Here we
note that Verma modules of g may not contain any simple module when restricted
to a reductive subalgebra k in general.
In this article, using the geometry of K_C orbits on the generalized flag
variety G_C/P_C, we give a necessary and sufficient condition on the triple
(g,k, p) such that the restriction X|_k always contains simple k-modules for
any g-module lying in the parabolic BGG category O^p attached to a
parabolic subalgebra p of g.
Formulas are derived for the Gelfand-Kirillov dimension of any simple
k-module occurring in a simple generalized Verma module of g. We then prove
that the restriction X|_k is multiplicity-free for any generic g-module X \in O
if and only if (g,k) is isomorphic to a direct sum of (A_n,A_{n-1}), (B_n,D_n),
or (D_{n+1},B_n). We also see that the restriction X|_k is multiplicity-free
for any symmetric pair (g, k) and any parabolic subalgebra p with abelian
nilradical and for any generic g-module X \in O^p. Explicit branching laws are
also presented.Comment: 31 pages, To appear in Transformation Group
Bogoliubov Theory and Lee-Huang-Yang Corrections in Spin-1 and Spin-2 Bose-Einstein Condensates in the Presence of the Quadratic Zeeman Effect
We develop Bogoliubov theory of spin-1 and spin-2 Bose-Einstein condensates
(BECs) in the presence of a quadratic Zeeman effect, and derive the
Lee-Huang-Yang (LHY) corrections to the ground-state energy, sound velocity,
and quantum depletion. We investigate all the phases of spin-1 and spin-2 BECs
that can be realized experimentally. We also examine the stability of each
phase against quantum fluctuations and the quadratic Zeeman effect.
Furthermore, we discuss a relationship between the number of symmetry
generators that are spontaneously broken and that of Nambu-Goldstone (NG)
modes. It is found that in the spin-2 nematic phase there are special
Bogoliubov modes that have gapless linear dispersion relations but do not
belong to the NG modes.Comment: v3: 62 pages, 18 figure
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